2-ways are primarily a diesel application. After 1981, 3-ways became the standard for gasoline to reduce nox emissions.
You want to open that up a little bit, but not by much. The 3.0 crossover flow is choked down, where burning the #4 and #6 exhaust valves became a typical problem. Headers are a popular workaround for that.
I'm just a 4-banger Yota head. <img src="/forums/images/graemlins/smile.gif" alt="" />
You're out on Eielson aren't you? <img src="/forums/images/graemlins/notooth.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />
Cat trivia:
A three-way catalytic converter has three simultaneous tasks:
Reduction of nitrogen oxides to nitrogen and oxygen.
Oxidation of carbon monoxide to carbon dioxide.
Oxidation of unburnt non-methane hydrocarbons (HC) to carbon dioxide and water.
Since 1981, three-way catalytic converters have been at the heart of vehicle emission control systems in North American roadgoing vehicles, and are also used on "Large Spark Ignition" engines. LSI engines are used in forklifts, aerial boom lifts, ice resurfacing machines, and construction equipment.
A two-way catalytic converter has two simultaneous tasks:
Oxidation of carbon monoxide to carbon dioxide.
Oxidation of unburnt non-methane hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide and water.
This type of catalytic converter is commonly used on diesel engines to reduce hydrocarbon and carbon monoxide emissions. They also were used on spark ignition (gasoline) engines in automobiles up until 1981, when they were replaced by three-way converters due to regulatory changes requiring reductions on NOx emissions.
